1. Technical Field
Embodiments of the present invention relate to systems and methods for cooling a device. Embodiments of the invention more particularly relate to a cooling device and a projector and cooling the projector.
2. Related Art
Recently, small-sized cooling devices have been proposed that cool a device by absorbing the heat of a heat producing device using a liquid cooling medium.
For example, a projector may include a solid-state light emitting source that has high responsiveness for a supplied signal and superior dimmer control. While the amount of light emitted by a solid-state light emitting source (a heat producing body) increases in proportion to the amount of a supplied current, the amount of heat produced increases as well. Thus, a solid-state light emitting source is damaged or its lifetime is shortened due to the heat produced in a case where a large current is supplied to the solid-state light emitting source. Accordingly, technology for suppressing the damage to the solid-state light emitting source and lengthening the lifetime of the solid-state light emitting source by cooling the solid-state light emitting source is needed.
Conventionally, a cooling device includes a cooling medium that is used for cooling a heat producing source such as the solid-state light emitting source. A cooling medium cooling unit cools the cooling medium whose temperature is high due to absorption of the heat produced by the heat producing source.
For example, in JP-A-8-242463 discloses a technology for resolving uneven temperatures inside a cooling bath by constantly circulating a cooling liquid (cooling medium) using a circulation mechanism. By utilizing such a technology, a current or a voltage applied to a solid-state light emitting source can be raised, which raises the screen luminance, without destroying the solid-state light emitting source. Thus, an increase in the size of a projector device is not necessary. In addition, the liquid amount of the cooling liquid can be increased. Furthermore, the heat of the heated cooling liquid can be radiated to the outside with high efficiency using the cooling mechanism and the cooling efficiency can be improved.
In a liquid cooling jacket disclosed in JP-A-8-242463 that cools a semiconductor module disposed in an electronic apparatus or the like, a sealed-system circulation flow passage is formed which circulates cooling water in a sealed state to prevent leakage of the cooling water (see FIG. 12A). However, when a pump is operated, as shown in FIG. 12B, the volume of the sealed-system circulation flow passage expands based on deformation of a constituent element of the sealed-system circulation flow passage due to pressure raised in accordance with fluid resistance of the flow passage. The degree of the expansion on the upstream side (pump outlet-side flow passage side) is higher than that on the downstream side (pump inlet-side flow passage side) due to the influence of the addition of the flow resistance on the downstream side. Accordingly, when such driving is continued, the pressure applied at the supply side becomes negative pressure, and the pumping characteristics deteriorate. As a result, the pump cannot stably circulate the cooling water, and there is a concern that it will become difficult to stably cool a heat producing device.
The degree of the expansion is discussed below.
First, the amount of increase in the volume of the entire flow passage system at the time of applying constant pressure ΔP to the entire circulation flow passage system is assumed to be ΔV.
Next, a pressure difference between the pressure at the upstream side and the pressure at the downstream side in a case where a fluid of a desired flow amount flows in the circulation flow system is assumed to be Ps. Toward the downstream side of the circulation flow passage, the pressure of the inside of the circulation flow passage decreases so as to be Ps=0 at the pump inlet-side flow passage. At this time, in a case where the amount of the fluid in the entire circulation flow passage is constant, the circulation flow passage is deformed on the upper stream side of the circulation flow passage so as to increase the volume Vd. Accordingly, the fluid is insufficient on the downstream side and results in a negative pressure state.
Systems and methods for maintaining the pressure at the pump inlet-side flow passage to be the same as that before driving the pump without generating negative pressure is needed.